The boson peak and its relation with acoustic attenuation in glasses

Experimental results on the density of states and on the acoustic modes of glasses in the THz region are compared to the predictions of two categories of models. A recent one, solely based on an elastic instability, does not account for most observations. Good agreement without adjustable parameters is obtained with models including the existence of non-acoustic vibrational modes at THz frequency, providing in many cases a comprehensive picture for a range of glass anomalies.

The full widths hΓ of x-ray Brillouin spectra measured on six glasses in function of the mode energy E. The red curves are calculated using a model solely based on an elastic instability. The green lines of slope 4 are derived from the Soft Potential Model, terminating then at the EIR values obtained from the experimental data. Arrows indicate the approximate boson-peak positions.